The Evocation Wizard's 14th level ability Overchannel says (in part):
When you cast a wizard spell of 5th level or lower that deals damage, you can deal maximum damage with that spell.
I assume you compute the maximum damage and then if there is a save and the creature makes it, they take half of the maximum, but as written, it kind of sounds like you can deal maximum damage without allowing a save.
Spells don't actually specify when the damage is "dealt" (before or after the save). They typically say that the creature "takes" ndX points of (some type of) damage, or half on a successful save. If damage isn't "dealt" until it is "taken" then you would read this as "you deal ndX points points of (some type of) damage, or half on a successful save" and the amount that "you deal" (being that long ndX or half on a save clause) is replaced by "maximum damage".
RAI, I'm sure they are still supposed to get their save for half. But RAW I don't think it is actually that clear.